De Sitter (Moon)

Named after Willem Sitter - Dutch astronomer (1872-1934).

De Sitter is a lunar crater that is located near the northern limb , to the north of the Baillaud–Euctemon crater pair. Due to its location, this crater appears very foreshortened when viewed from the Earth, limiting the detail that can be viewed. The crater also receives sunlight at a low angle, when it is on the sunlit side. This crater forms part of an unusual three-crater cluster, with De Sitter overlying the northeast rim L and the southern rim M. All three craters are of comparable dimension, with the largest being De Sitter M. Where De Sitter overlies the other two craters, its outer rim appears slumped. (wikipedia entry)

A crater is a circular depression likely created by an impact event. On the Moon they are named after deceased scientists, polar explorers, astronauts or cosmonauts.